ARM: dts: imx: add alias for gpio

Add alias for gpio nodes, so that gpio driver can identify the port
number and then specify a sensible gpio base rather than using the
one dynamically allocated by gpio core.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/imx51.dtsi

@@ -17,6 +17,10 @@
 		serial0 = &uart1;
 		serial1 = &uart2;
 		serial2 = &uart3;
+		gpio0 = &gpio1;
+		gpio1 = &gpio2;
+		gpio2 = &gpio3;
+		gpio3 = &gpio4;
 	};
 
 	tzic: tz-interrupt-controller@e0000000 {